High-Throughput Cell Concentration Using A Piezoelectric Pump in Closed-Loop Viscoelastic Microfluidics

Abstract

Cell concentration is a critical process in biological assays and clinical diagnostics for the pre-treatment of extremely rare disease-related cells. The conventional technique for sample preconcentration and centrifugation has the limitations of a batch process requiring expensive and large equipment. Therefore, a high-throughput continuous cell concentration technique needs to be developed. However, in single-pass operation, the required concentration ratio is hard to achieve. In this study, we propose a closed-loop continuous cell concentration system using a viscoelastic non-Newtonian fluid. For miniaturized and integrated systems, two piezoelectric pumps were adopted. The pumping capability generated by a piezoelectric pump in a microfluidic channel was evaluated depending on the applied voltage, frequency, sample viscosity, and channel length. The concentration performance of the device was evaluated using 13 μm particles and white blood cells (WBCs) with different channel lengths and voltages. In the closed-loop system, the focused cells collected at the center outlet were sent back to the inlet, while the buffer solution was removed to the side outlets. Finally, to expand the clinical applicability of our closed-loop system, WBCs in lysed blood samples with 70% hematocrit and prostate cancer cells in urine samples were used. Using the closed-loop system, WBCs were concentrated by ~63.4 ± 0.8-fold within 20 min to a final volume of 160 μL using 10 mL of lysed blood sample with 70% hematocrit (~3 cP). In addition, prostate cancer cells in 10 mL urine samples were concentrated by ~64.1-fold within ~11 min due to low viscosity (~1 cP).

Separation and Washing of Candida Cells from White Blood Cells Using Viscoelastic Microfluidics

“…Compared to other passive methods using Newtonian fluids, viscoelastic particle/cell manipulation can be achieved in a simple straight microchannel due to the non-uniform distribution of the first normal stress difference (N 1 ) [21], eliminating the need for complicated channel structures. Therefore, viscoelastic microfluidics has been applied to the focusing [21,22], separation [23][24][25][26][27], concentration [28,29], and washing of particles/cells [19].…”

Continuous On-Chip Cell Washing Using Viscoelastic Microfluidics

“…Although inertia-based cell washing can be achieved in a straight channel, the flow rate range and cell size required for efficient washing are limited. Owing to the advantages of viscoelastic microfluidics, it has been applied to not only particle/cell focusing and separation [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ], but also particle/cell washing [ 24 , 25 , 26 ].…”